This invention relates to an engine ignition control and more particularly to an improved arrangement for controlling the spark timing of an engine during start-up conditions.
As is well known, spark-ignited internal combustion engines incorporate a spark advance system which is provided for controlling the time of firing of the spark plug in response to engine running conditions. As should be readily apparent, the optimum time of spark plug firing is important to ensure good engine performance.
It is well known that the optimum spark timing for an engine depends upon a variety of factors and primarily upon the load on the engine and the engine speed. Therefore, many types of conventional engine ignition systems include a spark advance mechanism that interrelates with the throttle valve of the engine so as to adjust the spark timing in response to the throttle valve position. The throttle valve position is directly related to the engine load, as should be readily apparent.
Most of these spark timing systems include a linkage system that is interrelated between the throttle mechanism and the spark advance mechanism. The spark advance mechanism normally includes a pulser coil mounted on a timing plate in proximity to the engine output shaft. This timing plate is rotatably adjusted and cooperates with a permanent magnet affixed to the engine output shaft for generating a pulse signal at a specific crankshaft angle. By interrelating the movement of the timing plate and the throttle valve, the appropriate spark timing may be generated for a given engine load condition.
Although these systems are particularly useful and effective, there are some running conditions wherein the spark timing provided by this mechanism is not optimum.
For example, when starting a cold engine it is frequently the practice to maintain the engine throttle valve in a partially opened condition. This provides more rapid warm-up and smoother running during the warm-up phase. However, when the spark timing is interrelated with the throttle control, then the spark timing at warm-up will not be the appropriate spark timing.
It is, therefore, a principal object of this invention to provide an improved spark timing control for an internal combustion engine.
It is a further object of this control to provide a relatively simple and yet highly effective spark timing control for an engine wherein the spark timing may be optimally set during starting and warm-up conditions.
It is a further object of this invention to provide improved spark timing control and method for an engine for operation during starting and warm-up which will provide the desired degree of spark timing and regardless of the position of the throttle valve.